I've replumbed my house overhead after a spate of under-slab leaks. I used CPVC, terminated by 90 degree CPVC-to-copper transition drop-ear elbows to 1/2" FPT. These things lurk well behind the drywall. I'm using a copper male adapter and a short length of copper pipe to get out to where the stops will be. I figured it'd be no problem using a deep socket to tighten the male adapter, but didn't anticipate that the hex on the copper male adapter is something like 27/32" or maybe 21.5mm -- nothing near any standard wrench I've got in a pretty extensive collection. Obviously I haven't collected the "right" wrench for these things -- is there some special deep socket-like thingy that's sold only in expensive to-the-trade stores only? Or does anyone have a suggestion? I've thought of soldering another fitting (maybe the stop, although I wanted to use compression fittings on them) on the outside end of the 3" pipe and using that fitting to tighten the inner fitting, but I'm not excited about that. Basin wrench would work, but I don't want to tear up the wall. Suggestions welcome.

You could make the connection with a brass nipple which would be strong enough to screw into the drop elbow. I suppose you could put a fitting on the copper, even temporarily, but I don't like to twist copper tubing.

If you do that you could use a piece of Type L tubing. A good joint with 95/5 tin/antimony solder (that's the kind legal for potable water) should take about as much torque as the tube.

I thought about using a nipple, but then I'd have to exchange all the stops for FPT connections, and of course buy those expensive nipples. Of the 9 sites, I think I can get a Crescent wrench on 4 of them, though. I don't like twisting tubing much either.

It's too late now, but you should have used transitions that had the copper extension coming out of the wall. Now your best option is to exchange those stops and buy brass nipples for the ones that you cannot get to.

Well, I had the idea of a copper tube coming out of the wall, but didn't know that such a transition existed. Neither of the two big box stores carry them, and the local "pro" plumbing store as much as told me they didn't want my business. Guess I should have spent more time reading this forum.

I did prowl around some high-end homes under construction to see what the local pros do. They just nail CPVC drop-ear Ls or Ts (to provide for a hammer arrestor) to a crossmember and stick a piece of CPVC out the wall, which didn't impress me much. I also had a need to not have anything sticking out of the wall for a while, so the adapter/pipe combo made sense. I just made the (unwarranted) assumption that the adapters' hexes would match up with standard wrenches. These were Nibco, and there's a lot of variation among individual fittings.

Spent some quality time at the Sears Tool Center and found that a 13/16" 6-point is too small, 7/8" 6-point is too big, 21mm 6-point is too small, 22mm 6-point is sloppy, 21mm 12-point kinda-sorta fits. Found a really neat tool called the Armstrong Eliminator, a deep socket wrench which allows the bolt to pass completely through the socket (the ratchet surrounds the socket), but the same size problems show up there. Also, the copper tube was a scoshe too big to pass through the 22mm socket.

Seen 'em in print, never had one in my hand. As I remember, they don't come in a deep-socket, and the overall diameter may be a problem in a couple of places. I've also seen special-purpose very deep sockets which look like they were made out of a piece of pipe with a hex mashed into one end, and a hole through the other end for a handle, but haven't found a wide selection in one place. If I get desperate, I think I could make one of these myself. Good excuse to buy a TIG welder, maybe.

...brass nipples are just brass nipples. But a TIG welder, now THERE's a TOOL!

Original problem is solved. Instead of matching the tool to the adapters, I matched the adapters to the tool. Remembering that the variation among adapters was significant (let's hear it for QC), I took the 21mm 12-point socket to the big-box store and found 9 adapters that fit nicely. I was also able to get by with a piece of tubing short enough that the Sears deep socket was deep enough.

Pressure test of the hot-water side was successful, so today we have hot water at the kitchen sink, dishwasher, and laundry room, which my wife assures me is a Good Thing.

The bad news, of course, is that now I need another excuse to buy the welder.